Evolution - 5.1 Evolution Evidence Flashcards
Understandings:
- Evolution occurs when heritable characteristics of a species change
- The fossil record provides evidence for evolution
- Selective breeding of domesticated animals shows that artificial selection can cause evolution
- Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function
- Populations of a species can gradually diverge into separate species by evolution
- Continuous variation across the geographical range of related populations matches the concept of gradual divergence
Evolution =
changes over time -> in living organisms = change refers to the heritable characteristics of a species (= biological evolution)
Evolution involves a genetic changes
= the result of mutations or the selection of different allele combinations
–>
therefore: heritable characteristics are encoded for by genes and may occur within a population between generations as alleles
definition for biological evoltuion:
cumulative changes that occur within a population between generations
simplified:
a change in the allele frequency of a population’s gene pool over successive generations
microevolution =
small changes (eg cat ear shapes, colours) (and lead to the formation of a new breed/strain)
macroevolution =
big changes that also result in new species and even phylum
selective breeding
(examples on bioninja!)
a form of artificial selection (in which man intervenes in the breeding of species to produce desired traits in offspring)
therefore:
thing with desired trait + thing with desired trait = trait’s frequency increases throughout generations
- selective breeding = provides evidence of evolution as targeted breeds can show signif. variation in a relatively short time
Comparative anatomy
Comparative anatomy of groups of organisms may show certain structural features that are similar = implying common ancestry
Comparative anatomy - HOMOLOGOUS STRUCTURES:
= anotomical feathers that are similar in basic structure despite being used in diff ways
-> more similar they are between 2 species = more likely to be more closely related
HS illustrates = ADAPTIVE RADIATION = several new species rapidly diversify from an ancestral source with each new species adapted to utlitse a specific unoccupied niech
eg pentadactyl limb in diff animals (bioninja!)
Speciation:
in population, in species = gene variation -> normally, varialtion = continuous and follow a normal distribution curve as the rate of change is gradual and cumulative
= the evolutionary process by which 2 related populations diverge into separate species
Speciation - environmental effects:
(DEGREE OF DIVERGENCE)
If species becomes geographically split = experience different ecological conditions = overtime populations will adapt to the different conditions and gradually diverge
DEGREE OF DIVERGENCE = depends on extent of separation + time
- less = closer and recent
- more = further and longer
genetic divergence and genetic compatibility
as the genetic divergence between the relation populations increases, their genetic compatibility consequently decreases
-> eventually: 2 populations will diverge to an extent where if put in the same environment = can not longer intercreeed
WHEN THIS HAPPENS:
(= no interbreed and no fertile production) = CONSIDERED TO BE SEPERATE SPECIES
therefore, speciation = the evolutionary process by which 2 related populations diverge into separate species
Fossil evidence:
an example of how fossils prove evidence of evolution can be established by comparing hominin skeletons
eg
1. Australopithecus = haminin ancestor = first appeared (fossil record) approx 4 million years ago
2. (modern) homo sapiens = comparison (n) = demonstrates key evolutionary changes
Law of Fossil Succession
Fossils can be dated by determining the age of the rock layer (strata) in which the fossil is found
Sedimentary rock layers develop in a chronological order, such that lower layers are older and newer strata form on top
Each strata represents a variable length of time that is classified according to a geological time scale (eons, eras, periods)
Different kinds of organisms are found in rocks of particular ages in a consistent order, indicating a sequence of development
- Prokaryotes appear in the fossil record before eukaryotes
- Ferns appear in the fossil record before flowering plants
- Invertebrates appear in the fossil record before vertebrate species
This chronological sequence of complexity by which characteristics appear to develop is known as the law of fossil succession
This ordered succession of fossils suggests that newer species likely evolved as a result of changes to ancestral species
Transitional Fossils
While fossils may provide clues as to evolutionary relationships, it is important to realise that the fossil record is incomplete
1) Fossilisation requires an unusual set of specific circumstances in order to occur, meaning very few organisms become fossils
2) Only the hard parts of an organism are typically preserved, meaning usually only fragments of remains are discovered
3) With limited fossil data, it can be difficult to discern the evolutionary patterns that result from ancestral forms (‘missing links’)
Transitional fossils demonstrate the intermediary forms that occurred over the evolutionary pathway taken by a single genus
1) They establish the links between species by exhibiting traits common to both an ancestor and its predicted descendents
2) An example of a transitional fossil is archaeopteryx, which links the evolution of dinosaurs (jaws, claws) to birds (feathers)
3) As new fossils are discovered, new evolutionary patterns are emerging and old assumptions are challenged
fossil record provides evidence when:
something demonstrates a change in characteristics from an ancestral
(by revealing the features of an ancestor for comparison against living decesdants)
Cabon datings vs postassim/Argon (K/Ar)
Carbon-14 can be used for dating things but has a half-life 5,700 years = runs out
postassim/Argon (K/Ar) 1/2 life of 1.3 billion years
fossil =
perseved remains or traces of any organism from the remote past
1. preserved remains (body fossils) = direct evidence of ancestral forms and include: teeth, shells, bones
2. traces provide indirect evidence of ancestral forms and include: footprints, toothmarks, etc
to tality of fossils = both discovered and undiscovered = refers to fossil record = shows that over time changes have occurred in the deathers of living organisms (= evolution)
Transitional Fossils pt 2
Fossils can show gradual evolutionary changes with the intermediary forms that occurred over the evolutionary pathway taken by a single genus
fossil evidence for horse ancestor
horse breakdown = pg 2 of booklet
Selective Breeding
= shows how artificial selection can cause evolution
1) horse breeding
2) cow breeding
3) dog breeding
Homologous structures (and common ancestors)
= the evolutionary relationships between groups of organisms is determined mainly by structural similarities = HS = suggests they all descended from a CA w/ that feature
Homologous structures and adaptive radiation
= AR = a type of divergent evolution where a common ancestor evolves into a large number of species to occus different niches
Homologous structures = EXAMPLE
Pentadactyl limb!!! the bones of the forelimb of vertebrates are composed of similar bones arranged in a comparable pattern = indicative of a common ancestry
limb = mammals, birds, amphibians, reptiles (over 300 million years ago) = EARLY LAND VERTEBRATES
Pentadactyl limb = limb with 5 fingers/toes
